Try posting at the local college (flyer or email) or the co-op/internship office. If you email though it's best to go through the school rather than try to obtain a list of emails and send it yourself. I know I tend to delete those without reading.

From a college perspective the biggest problem with startups was trying to find one. You had to know somebody who knew somebody to even hear about a startup, let alone apply. A few friends of mine applied to some really cool startups but I didn't find out about those until after I had accepted a position elsewhere.